The present invention relates to gas cylinders, and, more particularly, relates to safety valves that may be installed therein.
Gas cylinders typically hold under high pressure both toxic and non-toxic gases. These cylinders have a threaded port for the insertion of a conventional service valve for inputting and outputting gases. The service valve also has a pressure relief valve therein. The service valve is typically made of brass and has a threaded stem for insertion into the threaded port of the cylinder. A steel cap is typically placed over the service valve and threaded onto the outside of the bonnet for protecting the service valve from damage. Still the service valve is subject to damage when the cap is not screwed on, left off during use or otherwise exposed by negligence. If the service valve is broken off, the gas inside the cylinder can escape turning the cylinder into a rocket and possibly releasing hazardous gases at the same time.
U.S. Pat. No. 4,606,367 discloses a safety and service valve. As noted in this patent, a mechanical member in the upper body of the special valve extends into a ball chamber and constantly biases a ball to allow a clear flow path. If the upper body is broken away removing the mechanical member, the ball is spring biased into a closed position to block the flow path. The ball chamber is an integral part of the valve stem. Although this special valve serves the purpose for which intended, many gas cylinders in being do not have this special valve safety feature U.S. Pat. No. 1,625,044 discloses a valve rod with a handle thereon which contacts a ball valve which is normally biased closed. Upon breaking of the upper valve body, the ball valve would close preventing a gas leak. The ball valve is a part of the filler plug which goes into the bonnet of the cylinder. A discharge manifold is placed into the filler plug hole during use or recharge. The manifold and filler plug are separable and are only attached together when the cylinder is actually in use. This feature does reduce the chance of damage to the manifold during such use.
Thus, there is a need for a safety valve for conventional gas cylinders having a service valve thereon without a safety valve being an integral part thereof.